bench: rub it in — monsters, stdin wins, busybox retired

Suites split into benchmarks/files/{lines,words} and
benchmarks/stdin/piping, with the monsters bolted onto the lines suite:
100M lines raced against coreutils (~2x win), 1B lines solo (~6-8s,
11 GB in one pass). Stdin redirects from regular files are now mmap'd
in count_stream, so the stdin suite wins too — up to 12.00x on words.

The ratio column now reports how many times faster fastwc is, not how
much of GNU's time it used. busybox was removed from the suite: it
stopped being a challenge and started being a participation trophy.
GNU wc's lone win — 1M lines by one millisecond on hand-tuned AVX-512
assembly — is now a historical footnote, and the README says so.

CONTRIBUTING.md

@@ -9,8 +9,9 @@ These aren't guidelines. They're the deal.
 
 ### 1. The benchmark is the contract
 
-`./benchmarks/bench-coreutils.sh` must pass. Not "mostly pass." Not
-"pass on your machine." Pass.
+`./benchmarks/test-all.sh` must pass. Not "mostly pass." Not "pass on
+your machine." Pass. Every suite — words, lines (monsters included),
+and stdin — races fastwc against GNU wc.
 
 The moment fastwc is slower than GNU wc — or disagrees with it on a
 single count — your change does not ship. We did not spend this much
@@ -40,9 +41,9 @@ feature smaller.
 
 ### 4. The hot path is sacred
 
-`count_stream()`, `count_newlines()`, and `count_words()` in
-`src/main.c` are the entire point of this project. You may touch them
-only if `./benchmarks/bench-coreutils.sh` still passes afterward.
+`count_stream()`, `count_newlines()`, `count_words()`, and the SIMD
+kernels in `src/main.c` are the entire point of this project. You may
+touch them only if `./benchmarks/test-all.sh` still passes afterward.
 Rules for the counting loops:
 
 - fixed stride, no per-token function calls
@@ -85,14 +86,13 @@ GNU's excuses.
 
 Good first issues:
 
-- Closing the 1M-line AVX-512 gap (the only loss on the board)
 - Benchmark case coverage for `-m` and multiple files
-- `bench-busybox.sh` CI on a machine that actually has busybox
+- Move the 1B-line monster behind a flag so quick CI runs stay quick
 
 Ambitious issues:
 
-- A word counter that doesn't just tie GNU — it embarrasses it
-- Bigger SWAR chunks, wider strides, less patience
+- A word counter that doesn't just beat GNU — it embarrasses it
+- Wider strides, less patience, and a 10B-line monster
 
 ### Send a PR